1. Field of the Invention
This invention relates to a noise dampened canister vacuum cleaner.
2. Description of the Related Act
The typical central vacuum cleaner system for a home comprises a canister vacuum cleaner, known to those skilled in the art as the power unit, which creates a vacuum source, a fixed piping system which connects the power unit with outlets located in convenient locations throughout the house and portable flexible hosing which may be connected at one end to any of these outlets. The free end of the hosing is a remote source of the vacuum created by the power unit.
There are numerous advantages to the installation and use of a central vacuum system when a comparison is made to the use of a typical portable vacuum cleaner. These advantages result from, for example, the increased suction which may be created by a large, non-portable power unit, the elimination of the need to transport a vacuum power unit to the site requiring cleaning, the ease of maintenance and cleaning of central vacuum cleaning systems and the advantage of being able to exhaust dirty air (pre-filtered or not) to a remote location.
The power unit of a central vacuum system comprises the most complicated and costly component of the system. The main components of a typical power unit are a canister, an electric motor and an air pump driven by the motor, both located in the canister, a dirty air intake connected to the intake of the pump, an exhaust connected to the output of the pump and an air filter located between the dirty air intake and the pump. It is not necessary that the filtering means be included in the power unit itself. The power unit may simply deliver dirty air to a remote location where the dirty air may be filtered, or simply exhausted. In such systems, the pumping means should be adapted for pumping unfiltered air. Where the power unit includes a filtering means, it may comprise an air permeable diaphragm and filter bag used in combination. The diaphragm, typically made of cloth, provides support for the filter bag when in use. The bag is typically removable and disposable.
The air pump produces the vacuum which is required to draw dirty air into the canister, through the air filtering means and finally through the exhaust outlet. The air pump is usually a centrifugal fan.
The centrifugal fan typically consists of an impeller which rotates within a casing. The casing is usually cylindrical in shape; however, involute or shell-shaped casings are not unknown. The impeller usually consists of a number of blades mounted to a shaft to extend generally radially from the shaft, with the shaft projecting along the axis of the casing. In the case of a cylindrical casing, the casing may have an inlet end and a single exhaust port or several exhaust ports on its periphery. Typically, the air inlet to the casing is located near to the center of the impeller. The electric motor turns the pump shaft in order to rotate the impeller within the casing. The blades of the impeller, in revolving, produce a reduction in pressure near the center of the impeller. The air is thereby drawn through the air inlet, into the center of the impeller and is then forced outwardly along the impeller blades with an ever increasing tangential velocity. The velocity of the air as it leaves the outer portion of the blade tips is changed to a pressure head in its transfer to the casing, which in turn forces the air into the exhaust port or ports.
Increasing the speed of the rotation of the impeller results in a greater pressure head or an increased throughput of air through the impeller casing. This is a desirable characteristic in a vacuum cleaning system. An increase in impeller rotation is usually accomplished through the use of faster and more powerful electric motors to drive the impeller. Since central vacuum cleaners do not need to be designed for portability, they may be constructed with larger and therefore faster and more powerful motors to gain this desirable increase in suction. However, when operated at a faster speed, there is an increase in the noise level attributable in part to the air pump.
As noted above, the gain in speed of the air pump is usually accomplished through the use of a larger electric motor. Consequently, there is also an increase in the generation of noise level attributable to the electric motor.
The increase in the noise levels resulting from the larger electric motor and faster pump found in a central vacuum cleaner is an undesirable characteristic. Where the power unit of a central vacuum cleaner can be installed in a remote location, the high noise levels may be tolerable; however, where the installation of the power unit is made, for example, in the closet of a small apartment unit, an increase in noise level cannot be ignored.
It is an object of the present invention to provide a canister vacuum cleaner with means to dampen the noise attributable to the air pump.
Preferably the present invention provides means to dampen the noise attributable to the electric motor.
The use of any electric motor will result in a generation of heat. Such heat generation is the result of frictional losses in the motor in combination with heat generated by the conduction of electricity through the wire windings of the motor. This heat generation is more pronounced in larger and faster electric motors in comparison to their smaller counter parts.
It is known that the performance, and ultimately, the lifetime of an electric motor is generally inversely proportional to the ambient temperature in which it operates, if that ambient temperature is above the desired operating range of the motor. If an electric motor is often operated at a temperature higher than that for which it was designed, a breakdown of the materials which comprise the motor is to be expected as a direct result, and indirectly, through the breakdown of motor lubricants, expansion of moving parts to sizes outside their optimum tolerances, breakdown of insulative coatings, deformation of solid parts etc., a general deterioration of the motor is observed.
Preferably the noise dampening means of this invention for a canister vacuum cleaner is provided with a suitable manner for cooling the electric motor.